Summary

This module manages common properties of domains for one or more virtual hosts.
Specifically it can use the ACME protocol
(RFC Draft)
to automate certificate provisioning. These will be configured for managed domains and
their virtual hosts automatically. This includes renewal of certificates before they
expire. The most famous Certificate Authority currently implementing the ACME protocol
is Let's Encrypt.

Warning

This module is experimental. Its behaviors, directives, and
defaults are subject to more change from release to
release relative to other standard modules. Users are encouraged to
consult the "CHANGES" file for potential updates.

Simple configuration example:

TLS in a VirtualHost context

This setup will, on server start, contact
Let's Encrypt
to request a certificate for the domain. If Let's Encrypt can verify the ownership
of the domain, the module will retrieve the certificate and its chain, store it
in the local file system (see MDStoreDir)
and provide it, on next restart, to mod_ssl.

This happens while the server is already running. All other hosts will continue
to work as before. While a certificate is not available, requests for the managed
domain will be answered with a '503 Service Unavailable'.

Prerequisites

Certificate signup and renewal with Let's Encrypt requires your server to be
reachable on port 80 (http:) from the outside. The alternative method over
port 443 (https:) is currently disabled for security reasons (status from
2018-01-14).

The module will select from the methods offered by Let's Encrypt. If LE decides
at one point in the future, to re-enable it again, mod_md will
use it when suitable.

But for now, only the port 80 variant is available (termed "http-01"). Only
when LE can reach your server on port 80 will mod_md work for
you. For now, at least.

If you do not want to offer any sites on port 80 any more, you may leave it open
and redirect all requests to your https: sites instead. Use the
MDRequireHttps described below to do
that in a convenient fashion. This will continue to answer http: challenges
from Let's Encrypt.

Controls if the base server, the one outside all VirtualHosts should be managed by
mod_md or not. Default is to not do this, for the very reason that
it may have confusing side-effects. It is recommended that you have virtual hosts
for all managed domains and do not rely on the global, fallback server configuration.

Sets challenge types and their execution order when proving domain ownership.
The names are protocol specific.
The current ACME protocol version implemented by Let's Encrypt defines two challenge
types that are supported by mod_md. By default, it will try
the one on port 443 when available.

When you use mod_md to obtain a certificate, you become a customer of the CA (e.g. Let's Encrypt). That means you need to read and agree to their Terms of Service,
so that you understand what they offer and what they might exclude or require from you.
mod_md cannot, by itself, agree to such a thing.

In case of Let's Encrypt, their current Terms of Service are here.
Those terms might (and probably will) change over time. So, the certificate renewal might require you to update this agreement URL.

Let's Encrypt offers, right now, two such URLs. One for the real certificates and
one for testing (their staging area, at https://acme-staging.api.letsencrypt.org/directory).
In order to have mod_md use this testing service, configure your
server like this:

In 'auto' mode, mod_md will drive a Managed Domain's
properties (e.g. certificate management) whenever necessary. When a MD is not used
in any virtual host, the module will do nothing. When a certificate is missing, it
will try to get one. When a certificate expires soon (see
MDRenewWindow), it will
renew it.

In 'manual' mode, it is your duty to do all this. The module will provide the existing
certificate to mod_ssl, if available. But it will not contact the CA for signup/renewal.
This can be useful in clustered setups where you want just one node to perform
the driving.

The third mode 'always' is like 'auto', with the difference that
mod_md will not check if the MD is actually used.

Defines if newly requested certificate should have the OCSP Must Staple flag
set or not. If a certificate has this flag, the server is required to send a
OCSP stapling response to every client. This only works if you configure
mod_ssl to generate this (see SSLUseStapling
and friends).

The configured executable is run when Managed Domains have signed up or
renewed their certificates. It is given the names of the processed MDs as
additional arguments (after the parameters specified here). It should
return status code 0 to indicate that it has run successfully.

All the names in the list are managed as one Managed Domain (MD).
mod_md will request one single certificate that is valid for all these names. This
directive uses the global settings (see other MD directives below). If you
need specific settings for one MD, use
the <MDomainSet>.

There are 2 additional settings that are necessary for a Managed Domain:
ServerAdmin
and MDCertificateAgreement.
The mail address of ServerAdmin
is used to register at the CA (Let's Encrypt by default).
The CA may use it to notify you about
changes in its service or status of your certificates.

The second setting, MDCertificateAgreement,
is the URL of the Terms of Service of the CA. When you configure the URL,
you confirm that you have read and agree to the terms described in the linked
document. Before you do that, the CA will not hand out certificates to you.

There are two special names that you may use in this directive: 'manual'
and 'auto'. This determines if a Managed Domain shall have exactly the
name list as is configured ('manual') or offer more convenience. With 'auto'
all names of a virtual host are added to a MD. Conventiently, 'auto' is also
the default.

In this example, the domain 'www.example.org' is automatically added to
the MD 'example.org'. Similarly for 'example2.org' where 'auto' is configured
explicitly. Whenever you add more ServerAlias names to this
virtual host, they will be added as well to the Managed Domain.

If you prefer to explicitly declare all the domain names, use 'manual' mode.
An error will be logged if the names do not match with the expected ones.

This directive allows you to define a Managed Domain (MD) with specific
settings, different from the global MD* ones. For example, you can have
such an MD use another CA then Let's Encrypt, have its unique renewal duration
etc.

The ACME protocol provides two methods to verify domain ownership: one that uses
port 80 and one for port 443. If your server is not reachable by at least one
of the two, ACME will not work for you.

mod_md will look at your server configuration and try to figure
out which of those are available. Then it can select the proper ACME challenge
to create a certificate for your site.

However if you have some fancy port forwarding in place, your server may be
reachable from the Internet on port 443, but the local port that httpd uses is
another one. Your server might only listen on ports 5001 and 5002, but be reached
on ports 443 and 80. How should mod_md figure that one out?

With MDPortMap you can tell it which 'Internet port'
corresponds to which local port.

Example

MDPortMap 80:- 443:5002

This example says that the server is not reachable on port 80 from the outside, but
local port 5002 is the one responding to https: requests.

Defines what kind of private keys are generated for a managed domain and with
what parameters. The only supported type right now is 'RSA' and the only parameter
it takes is the number of bits used for the key.

The current (2017) recommendation is at least 2048 bits and a smaller number is
not accepted here. Higher numbers offer longer security, but are computationally more
expensive, e.g. increase the load on your server. That might or might not be an
issue for you.

Other key types will be defined in the future.

Example

MDPrivateKeys RSA 3072

Please note that this setting only has an effect on new keys. Any existing
private key you have remains unaffected. Also, this only affects private keys
generated for certificates. ACME account keys are unaffected by this.

If the validity of the certificate falls below duration, mod_md
will get a new signed certificate.

Normally, certificates are valid for around 90 days and mod_md will renew
them the earliest 33% of their complete lifetime before they expire (so for
90 days validity, 30 days before it expires). If you think this is not what
you need, you can specify either the exact time, as in:

Example

When in auto drive mode, the module will check every 12 hours at least
what the status of the managed domains is and if it needs to do something.
On errors, for example when the CA is unreachable, it will initially retry
after some seconds. Should that continue to fail, it will back off to a
maximum interval of hourly checks.

This is a convenience directive to ease http: to https: migration of
your Managed Domains. With:

Example

MDRequireHttps temporary

you announce that you want all traffic via http: URLs to be redirected
to the https: ones, for now. This is safe and you can remove this again at
any time.

The following has consequences: if you want client to no longer use the
http: URLs, configure:

Permanent (for at least half a year!)

MDRequireHttps permanent

This does two things:

All request to the http: resources are redirected to the
same url with the https: scheme using the 301
status code. This tells clients that this is intended to be forever and
the should update any links they have accordingly.

All answers to https: requests will carry the header
Strict-Transport-Security with a life time of half a year.
This tells the browser that it never (for half a year) shall use http:
when talking to this domain name. Browsers will, after having seen this, refuse
to contact your unencrypted site. This prevents malicious middleware to
downgrade connections and listen/manipulate the traffic. Which is good. But
you cannot simply take it back again.

You can achieve the same with mod_alias and some
Redirect configuration,
basically. If you do it yourself, please make sure to exclude the paths
/.well-known/* from your redirection, otherwise mod_md
might have trouble signing on new certificates.

If you set this globally, it applies to all managed domains. If you want
it for a specific domain only, use:

Defines where on the local file system the Managed Domain data is stored. This is
an absolute path or interpreted relative to the server root. The default will create
a directory 'md' in your server root.

If you move this and have already data, be sure to move/copy the data first to
the new location, reconfigure and then restart the server. If you reconfigure
and restart first, the server will try to get new certificates that it thinks
are missing.

Notice:This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.